The present invention resides generally in the field of medical technology and more particularly relates to apparatuses and methods for deploying medical implants, especially frameless valves, within the vascular system.
It is well understood in human pathology that the proper functioning of cardiac and venous valves is of the utmost importance. Numerous studies have shown that diseased cardiac valves cause significant morbidity and mortality and that incompetent or destroyed venous valves often result in adverse medical conditions, especially in the lower extremities.
By preventing retrograde blood flow, the valves found throughout the venous system assist the flow of blood through the veins and returning to the heart. Venous valves are usually of the bicuspid type, with each cusp or leaflet forming a reservoir for blood, which, under pressure, forces the free edges of the cusps together to permit mostly antegrade blood flow to the heart. As a majority of venous blood flow is against gravity while a person is standing, incompetent or destroyed venous valves can cause significant medical problems in the legs, ankles, and feet. There are at least two chronic venous diseases in which venous valve incompetence is thought to be an important factor: chronic venous insufficiency and varicose vein syndrome.
Chronic venous insufficiency involves venous hypertension and chronic venous stasis due to valvular incompetence. It has been estimated that in the United States chronic venous insufficiency associated with skin changes and ulcers affects six to seven million people. Varicose vein syndrome involves vein dilation or enlargement. According to another estimate, varicose veins affect about 4% of the adult western population, and approximately half of this population has significant varicose vein syndrome for which treatment will be sought.
Turning now to the cardiovascular system, incompetent or destroyed heart valves are a common form of heart disease, the leading cause of death in the United States. Although reconstructive surgery has been shown to be superior to valve replacement surgery in some respects, it is difficult to perform and not always possible in every patient. As a result, the vast majority of patients with diseased heart valves undergo valve replacement surgery, which involves removing a native valve and replacing it with a prosthetic one. Prosthetic heart valves come in various shapes and sizes and can be formed with a variety of materials. Often, the design of a prosthetic valve depends on the characteristics of the valve being replaced (e.g., mitral, aortic, tricuspid, or pulmonary) and/or the size of the patient's heart.
To treat a condition of the vascular system, it may be desirable to deploy an artificial device, such as a valve, within a vascular vessel. Accordingly, a variety of artificial valves have been developed in the art for implantation within the vasculature. Likewise, a variety of delivery apparatuses and methods have been developed for deploying these and other devices. For example, U.S. Pat. No. 6,508,833 discloses a multiple-sided medical device that is pushed from a delivery catheter into the lumen of a duct or vessel, the device comprising a closed frame of a single piece of wire or other resilient material and having a series of bends and interconnecting sides. The device has both a flat configuration and a second, folded configuration that comprises a self-expanding frame. A covering of fabric or other flexible material is sutured or attached to the frame to form an artificial valve. The flexible material utilized in the disclosed valves can be comprised of collagenous submucosa obtained from various animals, such as, for example, pigs, cattle, and sheep. The submucosal material can be prepared in large, flat sheets, which are subsequently cut and attached to a framing element, for example a stent, for deployment in a vein.
There remain needs for improved and/or alternative apparatuses and methods for deploying artificial devices, and in particular frameless valves, within the vasculature. Advantageous deployment apparatuses would include at least one deployment member releasably engaged with at least one anchoring element. Advantageous deployment methods would effectively and efficiently deploy an artificial device. The present invention is addressed to those needs.